In recent times, the non-availability of an efficient method of reclaiming crude oil accidentally spilled from ocean tankers and the like has become very apparent. The "Exxon Valdez" disaster, in which 40 million liters of crude oil were released into the ocean, and the more recent "Mega Borg" disaster wherein in excess of 11 million liters were similarly spilled, illustrate the magnitude of the problem. In the case of the "Exxon Valdez", in addition to the financial loss from the lost production from the crude oil, the owners of the tanker spent more than $US2 billion in an attempt to clean up the spill and were also expected to be fined at least $US1.5 billion in penalties.
Current methods of attempting to clean up such spills include (1) the use of oil-skimming boats and containment booms; (2) bombarding the floating oil with chemical dispersants; and (3) bioremediation, whereby oil-consuming bacteria are dumped on the oil. However, none of these current methods are considered satisfactory as significant quantities of the oil spilled cannot seemingly be recovered or dispersed by any of these methods and pollution of the environment thus continues for many years afterwards.
Further, the more common chemical dispersion method is to use detergents which do not remove the offending spill but simply diminure the oil, making it seemingly less obvious and less insidious to the environment, which is not the true situation as damage to the environment still occurs. Also, the introduction of excessive quantities of detergents to a particular area is damaging in itself to the environment.
Another area where control of compounds, particularly liquid organic compounds, is required is the disposal and safe storage of toxic waste. At present, such toxic waste is usually contained in receptacles which are buried in the ground. However, receptacles are known to crack, rust or otherwise leak, thus allowing seepage of dangerous chemicals into the environment.
An oil-well fire is yet another example of where control of an organic compound, in this case burning hydrocarbons, is extremely difficult with some fires taking many months to extinguish. The main problem is the intense heat associated with such a fire causing ready re-ignition of the remaining oil and thus associated volatile components.
Prior art approaches to overcome such problems include applying refrigerants such as solid or liquid carbon dioxide and liquid nitrogen to oil spills on water for the purpose of either solidifying the oil or manipulating its movement.
Yet other prior art methods comprise applying solid materials to absorb spilled liquid hydrocarbons. Materials have included straw, newspaper, expanded perlite and a number of polymers of various compositions and configurations.
With regard to the prior use of polymers, it has been recognised that a number of hydrocarbon polymers affect the viscosity characteristics of the hydrocarbon liquid in which they are dissolved. Dependent upon polymer concentration, the viscosity of the liquid can be varied from reducing viscosity to increasing viscosity to a rubbery semi-solid or solid.
However, it is recognised that relatively high molecular weight polymers dissolve very slowly and prior art approaches include contacting the polymer with the hydrocarbon at ambient to relatively elevated temperatures. Because many of the rubbery polymeric materials are relatively soft and resilient, they are extremely difficult and often impossible to comminute.
Nevertheless, prior art advances in this technology include U.S. Pat. No 4,420,400, which describes a process for bodying a liquid hydrocarbon by dissolving sufficient polymer therein to substantially increase its effective viscosity and thereby converting the liquid to a semi-solid gel or to a rubbery solid. Successful practice of this process requires that the polymer be cryogenically comminuted and applied to the hydrocarbon in association with a cryogenic refrigerant. The comminution problem is overcome by cryogenically cooling a polymer slab which is then cut into smaller pieces. A preferred group of polymers are of a relatively high molecular weight, at least 1,000,000.
International Patent Application No PCT/US86/02638 describes the preparation of stable-non-agglomerating and rapid dissolving particulate polymer compositions by chilling the polymer to a temperature below its glass transition temperature using an inert cryogenic refrigerant and comminuting the chilled and brittle polymer to form particles thereof. The polymer particles are maintained at a temperature below the glass transition temperature of the polymer and are mixed with a finely divided, solid coating agent. The coating agent must be a solid, must be non-reactive toward the polymer and must have a median particle diameter less than one tenth the median diameter of the polymer particles. The coating agent particles and the polymer particles are physically admixed while warming the mixture to and above the glass transition temperature of the polymer resulting in the coating agent forming a multi-layered shell around each polymer particle.
However, these approaches to oil-spill control have significant disadvantages including complex reaction conditions, long dissolution times, low temperatures required, storage of components in pressure vessels prior to use and consequent increased transportation costs.